Yalu River

“Korean Amnok River River between NE China and N. Korea. Some 491 mi (790. Km) long, it rises on the N border of N. Korea, then flows to Korea Bay. It is an important source of hydroelectric power and is navigable by smaller vessels for most of its course. It became a political boundary in the 14th cent. During the Korean War, as U.N. forces battled toward it in 1950, Chinese troops crossed it, in effect marking their entry into the war.”